Septic shock and septic multiple organ dysfunction/injury (MOD/I) are major causes of mortality among critically ill patients. Identifying new mechanisms and elucidating new pathways that lead to the development of septic shock and septic MOD/I may help to identify new target for developing novel therapies to treat these lifethreatening conditions. We recently discovered that endotoxemia or sepsis down-regulates Sp1 (specificity protein 1) DNA binding activity and depletes tissue Sp1 protein in rat and mouse lungs, which are accompanied by a reduced expression of two major Sp1-dependent housekeeping genes, eNOS and Cox-1. Because Sp1 mediates the transcriptional expression of hundreds of housekeeping genes whose products are important regulators of normal organ functions, are anti-inflammatory mediators, and are molecules participating in tissue repair, our finding leads us to hypothesize that Sp1 activity is protective against systemic inflammation and septic MOD/I, and that the Sp1-mediated protective mechanisms are repressed or diminished during sepsis, leading to exacerbated inflammatory and injury responses, promoting the development of septic shock and septic MOD/I. In supporting our hypotheses, we have demonstrated that preventing Sp1 degradation in vivo is associated with markedly decreased plasma and tissue levels of TNF-a, a significantly reduced iNOS and IL-[unreadable] protein expression and significantly increased IL- 10 expression in lungs of endotoxemic mice. The goals of this exploratory research project are to test the hypotheses stated above, and to prove the novel concept that endogenous Sp1 activity is protective against septic shock and septic MOD/I. We will alter endogenous Sp1 activity, and examine the effects of this alteration on systemic inflammation, organ injury and outcomes of lethal endotoxemia and sepsis. We will generate transgenic mice that overexpress a mutant human Sp1 gene encoding a LISPDE-resistant form of Sp1 protein (Specific aim 1). These transgenic mice will have normal issue levels of Sp1 protein and Sp1 activity during endotoxemia or sepsis. We will subject wild type and the transgenic mice (TG) to endotoxemia or CLP-induced sepsis, and compare the inflammatory and injurious responses, and mortality between the two mouse strains (Specific aim 2). We will demonstrate that mice with defective Sp1 activity (WT mice) will have exacerbated systemic and organ inflammation, more severe organ injury and higher mortality and that mice with intact or enhanced Sp1 activity (TG mice) will have less systemic and organ inflammation, ameliorated organ injury and reduced mortality during endotoxemia or sepsis. Completion of this project will prove the novel concept that endogenous Sp1 activity is protective against sepsis and endotoxemia, and open new avenues of investigation into the molecular mechanisms of septic MOD/I. Because Sp1 is a common mechanism controlling multiple anti-inflammatory pathways, our studies will provide experimental basis for boosting Sp1- mediated anti-inflammatory mechanisms as novel therapeutic strategies for treating septic shock and septic MOD/I. PUBLIC HEALTH RELEVANCE: Septic shock and septic multiple organ dysfunction/injury (MOD/I) are serious clinical syndromes that claim thousands of lives each year in the US. This research project is aimed at identifying new mechanisms and elucidating new molecular pathways that lead to the development of septic shock and septic MOD/I. Results from these studies will help to identify new target for developing novel therapies to treat these life-threatening conditions.